/*
 * Copyright (c) Kumo Inc. and affiliates.
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#pragma once

#include <cstddef>
#include <type_traits>

namespace melon {
    namespace detail {
        // Shortcut, so we don't have to use enable_if everywhere
        struct FormatTraitsBase {
            typedef void enabled;
        };

        // Traits that define enabled, value_type, and at() for anything
        // indexable with integral keys: pointers, arrays, vectors, and maps
        // with integral keys
        template<class T, class Enable = void>
        struct IndexableTraits;

        // Base class for sequences (vectors, deques)
        template<class C>
        struct IndexableTraitsSeq : public FormatTraitsBase {
            typedef C container_type;
            typedef typename C::value_type value_type;

            static const value_type &at(const C &c, int idx) { return c.at(idx); }

            static const value_type &at(const C &c, int idx, const value_type &dflt) {
                return (idx >= 0 && size_t(idx) < c.size()) ? c.at(idx) : dflt;
            }
        };

        // Base class for associative types (maps)
        template<class C>
        struct IndexableTraitsAssoc : public FormatTraitsBase {
            typedef typename C::value_type::second_type value_type;

            static const value_type &at(const C &c, int idx) {
                return c.at(static_cast<typename C::key_type>(idx));
            }

            static const value_type &at(const C &c, int idx, const value_type &dflt) {
                auto pos = c.find(static_cast<typename C::key_type>(idx));
                return pos != c.end() ? pos->second : dflt;
            }
        };
    } // namespace detail
} // namespace melon
